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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #296486
Title: Evolution of RXLR-class effectors in the Oomycete plant pathogen Phytophthora ramorum

Author
item GOSS, ERICA - University Of Florida
item Press, Caroline
item Grunwald, Niklaus - Nik

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2013
Publication Date: 11/7/2013
Citation: Goss, E.M., Press, C.M., Grunwald, N.J. 2013. Evolution of RXLR-class effectors in the Oomycete plant pathogen Phytophthora ramorum. PLoS One. 8(11):e79347. doi: 10.1371/journal.pone.0079347.

Interpretive Summary: Phytophthora plant pathogens contain many hundreds of effectors potentially involved in infection of host plants. Effectors are small proteins secreted by the pathogen that enter the host cell and affect a change in the plant host such as specific recognition with a cognate resistance gene. Comparative genomic analyses have shown that these effectors evolve rapidly and have been subject to recent expansions. We examined the recent sequence evolution of the largest effector gene families in the sudden oak death pathogen, P. ramorum. We found P. ramorum effectors have taken multiple evolutionary paths, including loss or gain of repeated domains, recombination or gene conversion among paralogs, and selection on point mutations. This work sheds new light onto the processes shaping the evolution of effectors in plant pathogens and thus sheds new light onto how pathogens and hosts coevolve.

Technical Abstract: Phytophthora plant pathogens contain many hundreds of effectors potentially involved in infection of host plants. Comparative genomic analyses have shown that these effectors evolve rapidly and have been subject to recent expansions. We examined the recent sequence evolution of RXLR-class effector gene families in the sudden oak death pathogen, P. ramorum. We found P. ramorum RXLR effectors have taken multiple evolutionary paths, including loss or gain of repeated domains, recombination or gene conversion among paralogs, and selection on point mutations. Sequencing of homologs from two subfamilies in P. ramorum’s closest known relatives revealed repeated gene duplication and divergence since speciation with P. lateralis. One family showed strong signatures of recombination while the other family has evolved primarily by point mutation. Comparison of a small number of the hundreds of RXLR-class effectors across three clonal lineages of P. ramorum shows striking divergence in alleles among lineages, suggesting the potential for functional differences between lineages. Our results suggest future avenues for examination of rapidly evolving effectors in P. ramorum, including investigation of the functional and coevolutionary significance of the patterns of sequence evolution that we observed.